1. Field of the Invention
The present invention generally relates to implantable medical devices, and in particular such medical devices allowing an early detection of heart failure in subjects.
2. Description of the Prior Art
The heart is an essential organ in humans and most animals, pumping blood throughout the human/animal body. As a consequence, it is fundamentally important that the mechanical pumping properties of the heart operate correctly.
Heart failure is a condition that can result from a structural or functional cardiac disorder that impairs the ability of the heart to fill with or pump a sufficient amount of blood through the body.
Today, ejection fraction (EF) is the measure most commonly associated with heart failure (HF) diagnostics. There is a large population of the heart failure patients who have a preserved ejection-fraction (HFPEF-HF with preserved EF, HFNEF-HF with normal EF, or DHF—diastolic heart failure), but still some two thirds of the heart failure population have a decreased ejection fraction. When the ejection fraction starts to drop to detectable levels, such as below 40%, the patient is already severely ill. The reason for this is that the body in general and the heart in particular have many ways to counteract the failing systolic function. This makes the ejection fraction drop only detectable quite late in the disease progression. As a consequence, it is difficult to spot the degradation before the patient has progressed long in the heart failure condition.
There is therefore a need for an early detection of heart failure that can be used instead of or as a complement to the more late ejection fraction based HF-detection.